There is a need to effectively use natural energies such as wind power and sunlight in order to achieve a low carbon society. However, the natural energies largely vary and produce instable output. To solve this, output equalization is studied by temporarily storing energy generated by the natural energy in an electric storage device.
The electric storage device requires high output and a large capacity and is therefore configured by a storage battery module that includes a plurality of secondary batteries (hereinafter referred to as cells) connected in series parallel. A secondary battery such as a lead battery or a lithium-ion battery needs to be appropriately used so as to prevent high-voltage charging or performance degradation due to over discharge. The storage battery module therefore must include a function that measures battery states such as voltage, current, and temperature.
FIG. 2 illustrates a configuration example of ordinary storage battery module M. As illustrated in FIG. 2, storage battery module M includes a plurality of cells C connected serially or in series parallel. Both ends thereof are connected to inverter In via relay box Sw to supply electric power to alternating current system AC.
Storage battery module M includes cell controller CC corresponding to a specified number of serially connected cells C. Cell controller CC measures states of a plurality of cells. A plurality of cell controllers CC are connected to battery controller BC. Battery controller BC acquires states of a plurality of cells from a plurality of cell controllers CC. Battery controller BC calculates a charging state (SOC: State of Charge) or a battery degradation state (SOH: State of Health) based on the acquired states of a plurality of cells and notifies a calculation result to host system controller SC.
Host system controller SC settles operation of cells from a viewpoint of energy saving, for example. A large, high-output facility may connect a plurality of storage battery modules M in parallel.
In FIG. 2, various types of information are exchanged between battery controller BC and cell controller CC and between cell controllers CC in storage battery module M. The communication therebetween may be wired. However, Patent Document 1 proposes changing wired communication to wireless communication between cell controller CC and battery controller BC and between cell controllers CC.
According to Patent Document 1, the wireless communication eliminates the need for insulation by a photocoupler used for the wired communication and can prevent insulation breakdown on battery controller BC or cell controller CC due to short-circuiting on an insulation element such as the photocoupler and prevent a short-circuit discharge on the secondary battery, improving the reliability. A communication antenna is provided at an opposing position of a module (corresponding to cell controller CC in FIG. 1) to be capable of preventing a communication failure due to interference of signals transmitted from the communication antennas.
Changing the wired communication to the wireless communication can reduce wiring costs, insulation costs for measures against high voltage, and installation costs. Further, it is considered to improve the degree of freedom concerning cell arrangement and storage battery module shapes.
Patent Document 1 uses the wireless communication for connection between the controllers (cell controller CC and battery controller BC) in a battery system. This system is hereinafter referred to as a wireless battery system.